Effect of lithium concentration on the thermal and optical properties ofLixMn2O4by photoacoustic measurements

Abstract

In the present work, pellets of Li x Mn 2 O 4 polycrystalline powder samples with x = 0.8, 0.9, 1.0, 1.1, and 1.2 are analyzed to understand the effect of lithium concentration on the thermal and optical properties, and the electronic structure of Li x Mn 2 O 4 predicted in an earlier work using full-potential linear muffin-tin orbital ͑FP-LMTO͒ method is experimentally verified. The experimental tool used for the determination of the thermal and optical properties is the well-known photoacoustic technique. The variation of thermal diffusivity with changing x values in Li x Mn 2 O 4 is extensively studied to explain the influence of lithium concentration on the thermal properties, and has been correlated with the structural asymmetry and defects in Li x Mn 2 O 4 . The optical absorption spectrum, being the signature of the electronic structure of materials, is recorded in the visible range ͑350-800 nm͒. Six prominent absorption peaks associated with the O 2p-Mn t 2g , O 2p-Mn e g , and Mn t 2g -Mn e g band transitions for Li x Mn 2 O 4 , with x ഛ 1, are observed experimentally, substantiating the electronic structure predicted by the FP-LMTO method. However, it is observed that there are more absorption peaks in the case of Li 1.1 Mn 2 O 4 and Li 1.2 Mn 2 O 4 , which is attributed to the structural distortion from pure cubic spinel structure to a mixture of spinel and tetragonal structures, which is verified by the x-ray diffraction spectra.

Thermophysical properties of LiCoO2–LiMn2O4blended electrode materials for Li-ion batteries

“…Thermal conductivity was found to decrease with delithiation, an opposite behaviour to that observed by Maleki et al 33 The available data on LiMn 2 O 4 composites show also inconsistencies with respect to the specific heat capacity which is reported in a similar range as for the LiCoO 2 composite, from 0.7 to 1.3 J g À1 K À1 . A particular study was performed by Lee et al, 39 in which the thermal diffusivity was studied with dependence of Li content and a comparative very low value was related to the Li 1 Mn 2 O 4 sample, a = 94 Â 10 À6 m 2 s À1 .…”

Electronic structure of the weakly coupled edge-sharing MnO4spin-\frac {5}{2} chain compound LiMnVO4: anab initiostudy

“…Calculated and experimental lattice parameters together with atomic internal coordinate parameters given in fractional coordinates (x, y, z). For the convenience of comparison, the position coordinates have been transformed according to the symmetry operators: (1) x, y, z; (2) −x, −y, z + 1/2; (3) −x, y, −z + 1/2; (4) x, −y, −z; (5) −x, −y, −z; (6) x, y, z − 1/2; (7) x, −y, z + 1/2; (8) −x, y, z; (9) x + 1/2, y + 1/2, z; (10) −x + 1/2, −y + 1/2, z + 1/2; (11) −x + 1/2, y + 1/2, −z + 1/2; (12) x + 1/2, −y + 1/2, −z; (13) −x + 1/2, −y + 1/2, −z; (14) x + 1/2, y + 1/2, −z + 1/2; (15) x + 1/2, −y + 1/2, z + 1/2; (16)…”

“…For instance, lithiummanganese oxide (LiMn 2 O 4 ) has a cubic spinel structure at room temperature, which has been widely investigated as a cathode material for rechargeable Li ion batteries [4], where equal numbers of Mn 3+ and Mn 4+ ions randomly distribute over the octahedral sites. The complicated structural transition and magnetic state of LiMn 2 O 4 have been under extensive study [5][6][7]. Another typical compound with the normal spinel structure is lithium-vanadium oxide (LiV 2 O 4 ), which has attracted great interest since its heavy-Fermiliquid behavior was discovered by Kondo et al [8].…”